<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        *{
            margin: 0;
            padding: 0;
            box-sizing: border-box;
        }
        div{
            border: 2px solid red;
            width: 200px;
        }
        .div1{
            height: 200px;
            padding: 20px;
        }
        .div2{
            height: 100px;
            width: 100px;

            /*margin: 50px;*/
        }

    </style>
</head>
<body>
<div class="div1">
    <div class="div2"></div>
</div>

<!--<div class="div3">aaa</div>-->
<!--<div class="div4">bbb</div>-->
<!--<div class="div5">ccc</div>-->

</body>
</html>